Identification of Disease Specific Molecule Associated with Liver of Patients with PBC. Patients with primary biliary cirrhosis (PBC) have autoantibodies to mitochondrial enzymes including pyruvate dehydrogenase. In addition, the liver of patients contains a molecule that, when stained with a mAb specific for PDH, is disease specific. The actual epitope of this mAb is unknown as is the molecule found in the bile duct of patients with PBC. To identify this molecule, we will immunoprecipitate liver homogenate from patients and controls with the disease specific mAb and a control mAb. This immunoprecipitate will be then analyzed using MALDI-TOF and peptide mapping by protease digestion.